Important note: Information in this article was accurate in 2006. The state of the art may have changed since the publication date.
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Wall Street Journal - April 16, 2006
Marilyn Chase
The virus being modified is Adenovirus 5, now used by Merck & Co. and the U.S. National Institutes of Health to make two leading experimental AIDS vaccines that are in tests. The virus works like a shuttle rocket carrying a payload of AIDS genes to spark an immune defense.
The problem: the Ad5 cold virus, while largely safe, is so common that 40% to 50% of people in wealthy countries and up to 90% of people in Africa have been exposed to it and are already immune. Pre-existing immunity could foil vaccines by blocking the virus before it delivers its payload.
So the Harvard team tricked the immune system by snipping off key surface features of Ad5 that the body would recognize and react against. Then they gave Ad5 a new face by transplanting features of a rare relative virus, Adenovirus 48, to which few people are immune.
The trick worked. In animal tests, the hybrid cold virus evaded pre-existing immunity, successfully delivering and drawing immune reactions against its payload of monkey AIDS virus genes, said the team's leader, Dan H. Barouch of the Harvard Medical School and Beth Israel Deaconess Medical Center in Boston.
The work, funded by a $19.2 million grant from the NIH, was reported online yesterday in the journal Nature.
In Leiden, the Netherlands, Crucell's chief scientific officer, Jaap Goudsmit, said the vaccine could be in human tests by late 2007, adding the technology can be adapted for malaria, tuberculosis and other vaccines. However, Dr. Barouch cautioned, "Much more work needs to be done before we know whether it will have practical utility."
To be sure, multiple hurdles stand in the way of an AIDS vaccine, which many scientists say is at least 10 years off.
"The proof of the pudding is always what happens in humans, but this is a promising start in the attempt to get around the problem of pre-existing immunity," said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, a unit of NIH.
Gary Nabel, director of the NIH Vaccine Research Center, said his AIDS vaccine using the regular Ad5 has met only "mild" interference from pre-existing immunity in tests so far. Still, he said the Harvard work "lets us build a diversified portfolio" of vaccines for AIDS, TB and Ebola.
A Merck scientist was unavailable for comment.
Write to Marilyn Chase at marilyn.chase@wsj.com
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